The invention pertains to apparatus for positioning and/or drying running webs such as webs of paper that have printing thereon. This apparatus is commonly referred to as air bars and they are located on opposite sides of the running web so as to hold the web suspended and without touching the air bars. Pressurized air issues from the air bars and is generally directed against the running web so as to floatingly suspend the running web.
Examples of the type of apparatus to which this invention pertain are shown in the U.S. Pat. No. 3,739,491, issued June 19, 1973 and entitled "High Velocity Air Web Dryer". Another example of prior art of this general type is shown in the U.S. Pat. No. 3,776,440 which issued Dec. 4, 1973 and entitled "Web Handling Apparatus". Still another example of the air bar itself is shown in the U.S. Pat. No. 3,549,070, issued Dec. 22, 1970 and entitled "Floatation of Sheet Material". The air bar shown in that patent, as in the present application, utilizes the Coanda effect which causes the air to issue from a slotted nozzle and then follow the contour of a Coanda surface to support the web by the air on the Coanda surface.
All of the above patents have been assigned to an assignee common with the present invention.
Air bars of the general type to which the present invention relate must distribute the air evenly throughout the length and width of the nozzle in order to provide the most desirable operating characteristics. Furthermore, as the slotted nozzles are usually very small, they are subjected to plugging by the foreign matter, such as dust found in the air passing therethrough. It is important to be able to quickly clean the nozzles and prevent down-time of the entire line of equipment in which these web handling devices are located.